The abnormal visual pathways that occur in animals with pigment deficits will be studied. Studies of the central visual pathways in Siamese cats will be continued, especially in order to determine how retinal abnormalities are related to geniculate abnormalities and to show how geniculate abnormalities may be related to cortical abnormalities. The detailed anatomical relationship of abnormally routed retinofugal axons will be studied, using cobalt chloride and 3H proline as axonal markers which can show the course of axons within the optic chiasm of albino mice and Siamese cats. The early development of the abnormality will be studied in several different species. The development of the eye cup, optic nerve and optic chiasm will be studied at the time that the fetal fissure is first closing and the retinal ganglion cells are sending the first axons into the central pathways.